Optical simulation applications such as aircraft flight simulation often employ an optical probe which is moved over a scale model of terrain at a variable altitude and which transmits an image of the terrain model to a sensor, e.g. a television camera. Optical scanning probes are comprehensively described in "Optical Scanning Probe Technology (Tutorial)" by Martin Shenker, Procedings of the Society of Photo-Optical Instrumentation Engineers, Simulators & Simulation, vol. 59, pp. 71-79 March, 1975.
For some time, there has been a need for an optical scanning probe having multiple field outputs in which each of the outputs is centered around its own center of perspective so that each output can be used relatively free of distortion relative to its associated display; each field having its own perspective axis and mapping around its own axis, rather than having the side fields imaged assymmetrically around the center of a central field of view.
In the past, when it was desired to present to the user of the simulator probe, e.g. to a helicopter pilot trainee, two fields of view, one forward and one to the side, two separate probes have been utilized, requiring, in addition to duplication of the probes, duplication of the model boards, gantries for positioning the probes, illumination systems and computer inputs.
Also in the past there have been wide-angle scanning probes in which the output has been divided among three sensors, e.g. television cameras. To display such a system to the observer without gross distortion, two different methods have been used in the past.
One method was to use T.V. projectors to project the three images onto one screen. Such systems have used a concave front projection screen usually of spherical or cylindrical shape with the observer at the center of curvature of the display screen. The other method utilized projection onto a single rear projection screen positioned at the focal surface of a single infinity display system.
In the front projection screen system gross amounts of assymmetric distortion correction had to be introduced in the T.V. electronics to correct the image for the side fields.
In the rear projection system a smaller amount of distortion correction was usually required but it was still assymmetric.
In the case where it was desired to present these outputs as three separate displays, each with its own axis, a large amount of assymmetric distortion correction had to be introduced into each display that did not have its axis parallel to the original probe axis.
This invention provides a single, wide field of view probe with an improvement that gives an observer multiple fields of view. Each of the output fields of view exhibits image quality, low altitude capability and mapping similar to that which is obtainable with separate probes. More than two output fields of view are possible with this invention as will be described hereinafter.
The customary scanning probe functions of pitch, roll, heading, focus (and tilt-focus when used) remain unchanged, and are introduced in a conventional manner.